The cabin air environment on an aircraft is is probably lower than in many confined spaces because modern airplanes have cabin air filtration systems equipped with HEPA filters.
HEPA or high efficiency particulate air filters have similar performance to those used to keep the air clean in hospital operating rooms and industrial clean rooms. These filters are very effective at trapping microscopic particles as small as bacteria and viruses. They are effective at capturing greater than 99percent of the airborne microbes in the filtered air. The majority of modern, large, commercial aircraft, which use a recirculation type of cabin air system, utilise HEPA filters. A small number of older aircraft types have filters with lower efficiencies.
How does it work? Well, while you may have been previously led to believe that cabin air circulates from take off until landing without the introduction of fresh air, this is not the case. Fresh air is continuously introduced during the flight, on some aircraft such as the A350 XWB it’s every 2-3 minutes. The cabin air is constantly flowing, fresh air enters via the top of the aircraft, passes through the HEPA filters and is pushed down to the floor, meaning the air in the aircraft does not stay stagnant.
As the ‘new’ air enters the cabin from outside, the same quantity of ‘used’ air from the cabin is expelled overboard via the pressurisation outflow valves, such that it is fully renewed/exchanged with fresh air about every two to three minutes. For comparison, air in hospital rooms and classrooms is exchanged about every 10 minutes and about 20 minutes in offices. The fresh air from outside the aircraft is naturally free from any pathogens at the high cruising altitudes where airliners operate.
Scientists agree that HEPA filters are highly effective at capturing everything from viruses to skin flakes, but the problem, explained by various scientists, is that passengers can still breathe in tiny floating droplets from another passenger seated nearby — before the air carrying those droplets can be vented out of the cabin and filtered — this is why, for extra protection, airlines have now implemented mandatory mask policies for all passengers and crew onboard.
In addition to the good quality cabin air, airlines should be implementing various measures in order to continue to push down the pandemic-related risks of air travel.
Measures include:
Physical distancing to the extent feasible and implementation of “adequate risk-based measures where distancing is not feasible, for example in aircraft cabins”;
Wearing of face masks by passengers and aviation workers;
Routine sanitation and disinfection of all areas with potential for human contact and transmission;
Health screening, which could include pre- and post-flight self-declarations, as well as temperature screening and visual observation, “conducted by health professionals”;
Contact tracing for passengers and aviation employees: updated contact information should be requested as part of the health self-declaration, and interaction between passengers and governments should be made directly though government portals;
Passenger health declaration forms, including self-declarations in line with the recommendations of relevant health authorities. Electronic tools should be encouraged to avoid paper;
Testing: if and when real-time, rapid and reliable testing becomes available.
Mask-wearing by passengers and crew will reduce the already low risk, while avoiding the dramatic cost increases to air travel that onboard social distancing measures would bring.
“The safety of passengers and crew is paramount. The aviation industry is working with governments to re-start flying when this can be done safely. Evidence suggests that the risk of transmission on board aircraft is low. And we will take measures—such as the wearing of face coverings by passengers and masks by crew—to add extra layers of protection. We must arrive at a solution that gives passengers the confidence to fly and keeps the cost of flying affordable. One without the other will have no lasting benefit,” said Alexandre de Juniac, IATA’s Director General and CEO.
*The author is an aviation analyst. Twitter handle: @AlexInAir